A lifting device and method is provided for lifting and turning a rotor during the erection process of wind turbine structure. The lifting device comprises a base unit with a mounting adapted to be mounted to an outer surface of the hub. The lifting device is able to turn the rotor using a pivotal lifting arm arranged between two end plates or a moveable trolley assembly arranged on a track of the base unit. A power pack unit or another power unit is used to power the turning unit which turns the rotor around a turning point into an installation position. The lifting point is preferably aligned with the center of gravity of the rotor for providing a balanced lift.